Distortion power factor

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The distortion power factor is used in power electronics to describe how the harmonic distortion of a load current decreases the average power transferred to the load. Distortion power factor is an important factor in the calculation of true power factor, which describes the decrease in average power transferred due to harmonics and to phase shift between voltage and current.

\mbox{distortion power factor} = {1 \over \sqrt{ 1 + \mbox{THD}_i^2}} = {I_{\mbox{1,rms}} \over I_{\mbox{rms}}}

THDi is the total harmonic distortion of the load current. This definition assumes that the voltage stay undistorted (sinusoidal, without harmonics). This simplification is often a good approximation in practice. I1,rms is the fundamental component of the current and Irms is the total current - both are root mean square-values.

The result when multiplied with the displacement power factor (DPF) is the true power factor or just power factor (PF):

\mbox{PF} = \mbox{DPF} {I_{\mbox{1,rms}} \over I_{\mbox{rms}}}

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